1. Field of the Invention
The present invention generally relates to the chemical arts generally to a method and device for loading a catalyst into chambers, more particularly to loading a catalyst into chambers associated with a small reactor which may be a microreactor. One microreactor which this method and device is suitable for is a microreactor for generating hydrogen gas by decomposing or reforming a hydrocarbon fuel.
2. Background of the Invention
The growing popularity of portable electronic devices has produced an increased demand for compact and correspondingly portable electrical power sources to energize these devices. Developments in robotics and other emerging technology applications are further increasing the demand for small, independent power sources.
At present, storage or rechargeable batteries are typically used to provide independent electrical power sources for portable devices. However, the amount of energy that can be stored in storage or rechargeable batteries is insufficient to meet the need of certain applications.
Fuel cells have potential as a replacement for some batteries. Because they can operate on very energy-dense fuels, fuel cell-based power supplies offer high energy-to-weight ratios compared with batteries. Fuel cells are of particular interest to the military, where significant efforts are being made to reduce the weight of power supplies that soldiers must carry to support high-tech, field-portable equipment. There is also considerable potential for utilizing fuel cell-based power supplies for commercial applications, particularly for portable applications, where small size and low weight are desirable.
A common fuel cell is a polymer electrolyte membrane fuel cell (PEMFC). PEMFC's are constructed of an anode and a cathode separated by a polymer electrolyte membrane. The polymer electrolyte membrane is also known in the industry as a proton exchange membrane Functionally, fuel cells generate electricity by stripping an electron off hydrogen and allowing the charged proton H+ to pass through the proton exchange membrane while the electron e-travels around the proton exchange membrane thereby producing a voltage.
The charged hydrogen proton then reacts with atmospheric oxygen to produce water. In some applications, generally smaller PEMFC under about 2 KW, the PEMFC can function as an “air-breather” (see generally U.S. Pat. No. 6,117,577 issued to Wilson). In an air-breather oxygen can typically be obtained from the ambient atmosphere, only a source of hydrogen must be provided to operate the fuel cell.
Hydrogen supplied to such a fuel cell can be provided in a gaseous form from a tank of hydrogen, or it can be generated by reformation. However, providing compressed hydrogen is not always a viable option, because of the substantial volume that even a highly compressed gas occupies. Liquid hydrogen, which occupies less volume, is a cryogenic liquid, and a significant amount of energy is required to achieve the extremely low temperatures required to liquefy gaseous hydrogen.
The hydrogen supply can also be generated by a steam reforming method or a partial oxidation method, using as feedstock hydrocarbons such as LPG, naphtha, gasoline, kerosene, alcohol, coal or natural gas composed principally of methane or non-hydrocarbons such as ammonia.
Catalysts are commonly used to facilitate reformation of hydrocarbons within a reactor. Catalysts are also often used to facilitate the combustion in a combustion chamber of a microreactor to supply thermal energy for the reformation process.
Incorporation of catalysts into a microreactors is commonly done by either packing the catalyst particles or pellets into a chamber, into cut channels in a chamber, or catalyst coating the walls of cut channels in a chamber. Metal foams, screens, mesh and wires are also commonly used as a support substrate for catalysts. However, one limitation of metal foam supported catalyst is the tortuous flow pattern created and the pressure drops and resistance associated therewith. Also, the incorporation of a catalyst coated metal foam substrate necessitates intimate contact between the foam and the reactor body to provide good heat transfer.
Another feature beneficial to a microreactor is a structure wherein flow channels are provided in the reactor to facilitate the flow of gases over the catalyst while minimizing pressure drop, and facilitating heat transfer.
Flow channels can be machined with CNC or EDM milling. However, both have limitations with the aspect ratios (length/height) that can be achieved. EDM is also an expensive technique not well-suited for mass production.
Therefore, it is a desideratum to provide a method and device for catalyst loading into a chamber such as a reactor, it is also a desideratum to provide a method and device for catalyst incorporation into a chamber, which provides for flow channels without expensive CNC or EDM milling.